Are we missing something about Tony Blair's departure from office? He concedes a new framework for Europe's government and then races overnight to the Vatican to consult the Pope. He tosses his seals of office to an acolyte and goes on to the Holy Land to continue his bloodthirsty crusade against the infidel. Is Blair auditioning for Charlemagne? Is he, as I have long suspected, a secret Knight of the Middle Way, an initiate into the mysteries of holy spin, pledged to return the Golden Waffle to the sacred sofa of SW1?

Wherever else was on Blair's mind was this past weekend it was clearly not Europe. The new treaty signed in Brussels was a clear change in the constitutional relationship between Britain, the other states of Europe and the central authority of the union. Any such change, Blair clearly undertook at the election two years ago, would be put in a referendum to the British people. He can squirm but he cannot pretend now that a link between the new treaty and his previous pledge is "completely and utterly absurd".

What was negotiated in Brussels was a new European framework, not a housekeeping measure. It replicates the failed 2004 constitution for the foreseeable future. There is to be a single European president and, de facto, a foreign secretary, with the dignities and authority to speak on Britain's behalf, make treaties, join the United Nations, carry a "legal personality" and have enforcement powers. There is to be a cross-border human rights charter covering labour and social policy from which a British opt-out will be subject to legal challenge.

Forty areas of regulatory authority are no longer subject to national veto and move to qualified majority voting, including transport, energy, sport and a further range of industry regulation. The new treaty even dilutes the original purpose of the union by dropping from its mission, at France's insistence, a commitment to "undistorted competition", a victory for the corporatist/protectionist Europe much favoured by the Franco-German axis.

Whether or not Britain has secured a cast-iron "opt-out" on law and order and social policy, to pretend that these are tidying up amendments is ludicrous. As the German chancellor, Angela Merkel, stated in a letter to her fellow leaders, the treaty is indeed a new version of the 2004 proposal. It incorporates previous treaties plus "the innovations resulting from the 2004 intergovernmental conference". This could not be more explicit. Merkel renamed the constitution a "treaty" only to relieve the leaders of the need to honour the letter of their commitment to referendums. That Blair should be party to this trick is sadly symbolic of his office, leaving with a broken promise concealed behind a slippery verbal mendacity. The point is not whether the treaty is more or less radical than Maastricht, which had no referendum, but that he promised one. Now, to say it would be like holding "a referendum on an open plan office" is an insult to the public.

Referendums are, of course, political oddities. They give an added layer of legitimacy to a government decision for which a general election mandate might seem inadequate. A classic referendum decision is over a constitutional change, such as the transfer of legislative and regulatory power from one tier of democracy to a subordinate or superior one. In the evolution of Europe such transfers have been continual and controversial, leading to ever greater demands for them to be referred to national electorates. To deny such participation is archaic, rooted in the oligarchic fallacy that some political decisions are too complex for mere plebeians to consider, let alone decide - long the outlook of Britain's "pro-Europe" lobby.

The new treaty turns the European Union from a ragbag of cross-cutting laws and authorities into one sovereign and legal entity. Matters such as planning, social services and local taxation may be delegated to national assemblies, much as national assemblies delegate them to provincial and local government. But the new fount of power is clearly the centre. It was such a transfer of power (notably on labour law and cross-border migration) that defeated the 2004 constitution in the French and Dutch referendums of 2005.

Short of dismantling the European Union, the case for a new treaty/constitution, call it whatever, is overwhelming. It is needed to embrace the morass of disciplines and protocols to incorporate 27 member states in a common economic enterprise. But the 2004 constitution was a linguistic and political outrage, a cobbled together Holy Roman Empire of a superstate, light years from the regulated trading compact of the treaty of Rome, an illiberal, protectionist and bureaucratic wasteland. It failed at the court of public opinion. Now to revive it and fob it off as a "tidying-up operation" is mendacious. If the people of Europe are content, let them say so. But to conceal it from them, to pretend that the treaty is not what it is, clearly for fear that they might not like it, marks a low point in the history of European democracy.

The referendum argument is not symmetrical. Those in favour of the treaty are against a referendum because they think they may lose it. They want Europe to stutter forward in secret ways that confirm the suspicion of all that emanates from Brussels. Others are for a referendum because they hope it will reject the treaty. But they at least have democracy on their side. They are ready to go out and argue the case and accept the result.

The issue is not whether the Brussels treaty is good or bad for Britain but whether the public believes it to be so. It may be that people are ready to shift another wide array of regulatory powers from Westminster to Brussels, though I very much doubt it. But let them say so clearly. Blair claims a referendum would "suck the political energy of the country for months". Why then did he promise it? What is democracy if not political energy? Was ever a statement so arrogant?

It is the proclaimed wish of the new prime minister, Gordon Brown, to listen to the public, to give it a new sense of control over its government. That is admirable. Brown has a clear manifesto commitment to hold a referendum on the new deal for Europe. Blair's last decision has been to renege on that pledge. It is scarcely credible that Brown's first will be to do so too.